1. Field of the Invention
The present invention relates to squibs or initiators and pyrotechnic ignition devices that are required to launch a projectile.
2. Description of the Related Art
Protective passive restraint or air bags used in automotive vehicles, escape slide chutes, life rafts and the like, are normally stored deflated and are inflated with gas at the time of need. Generally such devices are stored and used in close proximity to human beings. The devices, therefore, must be designed with a high safety factor that is effective at all times, during assembly as well as when stored and used.
Inflation is generally accomplished by means of an inert gas that is stored in a container under suitably high pressure. The gas may be further pressurized and supplemented at the time of use by the addition of high temperature combustion gas products that are produced by the burning of a gas generating composition.
Inflator assemblies for inflating an automotive vehicle occupant restraint or air bag are disclosed in U.S. Pat. Nos. 3,723,205, 3,714,807 and 5,131,680. The inflator assembly of U.S. Pat. No. 3,723,205 includes a container containing a gas under pressure. When there is need for an air bag or other inflatable device to be inflated, a squib is electrically actuated to ignite a gas generating composition. Burning of the gas generating composition causes an increase in the pressure in the container. This pressure increase is due to the gaseous products and heat provided by the burning of the composition. A rupturable burst disk is ruptured when a predetermined pressure is reached. The rupture of the burst disk enables gas to flow from the container to the air bag.
The inflator assemblies of U.S. Pat. Nos. 3,774,807 and 5,131,680 also include a container in which gas is stored under pressure. A gas generating valve releases the stored gas from the container and releases a supplementary gas into the stored gas from a gas generator after the stored gas has been released. This is accomplished by sending an electrical current through a squib. Such initiation of the squib results in an explosion that propels a projectile, specifically in U.S. Pat. No. 3,774,807 by a third member comprising a piston, and in U.S. Pat. No. 5,131,680 by a third member comprising an actuator assembly. In each case this propulsion opens an outlet port on the container which releases the stored gas. Supplementary gas from a gas generator is then released into the stored gas in the container, again by the propulsion of the respectively associated piston and actuator assembly.
The squib inflation systems of U.S. Pat. Nos. 3,714,807 and 5,131,680 differ from that of U.S. Pat. No. 3,723,205 by calling for the use of a movable piston or movable actuating member, specifically a projectile. The squibs used in the inflation systems of U.S. Pat. Nos. 3,714,807 and 5,131,680, and in such systems otherwise known in the prior art, do not use an integral projectile. Rather, they typically employ a separate projectile that is mechanically fastened to a third member to which the squib is also fastened. This, however, involves, for such squibs, a considerable extra expense for their production.
There is, thus, a need and a demand for an integral projectile squib which does not require a third member for attachment, and in addition, which is characterized in that the projectile may be attached to the squib body at almost any point in time prior to installation of the squib into the inflator, for example, of an automotive vehicle occupant restraint system. This feature makes transport and handling of the squib without the projectile attached much easier. The projectile also serves as a protective covering for the squib once it is installed.